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Aug. 15, 2012 -- People who have higher levels of the chemical bisphenol A (BPA) in their urine may be more likely to have narrowing of their coronary arteries, a new study shows.

BPA has been used for more than 40 years in food packaging, metal food and beverage can liners, and many other products. Nearly everyone has detectable levels of BPA, says researcher David Melzer, MD, PhD, professor of epidemiology and public health at England's University of Exeter.

Melzer's new study shows an association between urinary BPA levels and the width of the coronary arteries, which supply blood to the heart.

"The people who had narrowed arteries had higher levels of BPA in their urine," Melzer says.

The study, published in PLoS One, does not prove that BPA narrowed anyone's arteries. Many factors, including diet and activity, affect heart health.

Scientists from environmental groups say the study results add to growing evidence of a link between BPA and heart disease. A spokesperson from the chemical industry says it proves nothing.

BPA: FDA's View

The FDA has been studying BPA for several years, and in July, it banned BPA's use in baby bottles and sippy cups. Most of those products were already BPA-free, after makers stopped using BPA.

Some research, done in animals, has raised potential concerns that BPA exposure might lead to multiple health problems, such as diabetes, heart disease, and reproductive disorders.

However, the FDA has said that the evidence at this time does not suggest that the very low levels of exposure to BPA via the diet are unsafe.

BPA & Heart Disease: Study Details

The new study is the fourth led by Melzer's team to find the same link.

In one previous study, Melzer found that urinary levels of BPA helped predict who would be diagnosed with heart disease.

For the new study, Melzer evaluated 591 men and women in the U.K. All were evaluated for heart disease.

All had angiography, a test that uses dye and special X-rays to evaluate the health of the arteries.

Based on the angiography results, Melzer classified the patients as having normal arteries, or intermediate or severe coronary artery disease.

Of the 591:

385 had severe coronary artery disease.

86 has intermediate coronary artery disease.

120 had normal arteries.

"We only had 385 with severe [coronary artery disease],'' Melzer says. "Even in that relatively small group we found very clear evidence of a link of BPA exposure with coronary artery narrowing."

A greater percentage of those with intermediate and severe disease had higher urinary BPA levels, he found.

A fairly common level of urinary BPA, Melzer says, is 3 nanograms per milliliter or more.

While 17.5% of those with normal arteries had that level or higher, 30.2% of the intermediate group and nearly 27% of the severe group did, Melzer says. In those with severe disease, BPA concentrations were found to be higher compared to those without disease.

Melzer can't explain the mechanism behind the association. He found a link, not cause and effect.

BPA is thought to be excreted quickly from the body.

However, Melzer says, "BPA might be more active in the body than we previously thought.''

BPA is a complex chemical. "What we know is, it's absorbed from the gut and processed in the liver," he says. "How much goes through the liver without being processed is a matter of controversy. It seems to circulate in the blood and get into tissues."

Groups Respond

“Small-scale studies of this type tell us very little about potential impacts of BPA on human health," says Steven Hentges, a spokesman for the American Chemistry Council.

"This study is incapable of establishing a cause-and-effect relationship between BPA exposure and coronary artery disease. While studies like these can help provide direction for potential future research, by themselves they cannot and do not demonstrate that a particular chemical can cause a particular disease.''

The new findings add to growing evidence of the BPA-heart disease link, says Sonya Lunder, MPH, senior research analyst at the Environmental Working Group.

She says the researchers are ''knitting together a compelling case about this everyday toxin that could affect the lives of millions."

The evidence of a link is becoming stronger, agrees Sarah Janssen, MD, PhD, MPH, senior scientist at the Natural Resources Defense Council. In March, the FDA rejected NRDC's request to ban BPA in all food packaging.

For those wishing to reduce exposure to BPA, Lunder has these tips:

Avoid eating canned food or beverages.

Use glass or stainless steel water bottles.

Keep store receipts, which can have BPA as a coating, out of grocery bags.